Regulation of Polarized Traffic by PI-Metabolizing Enz

具有不同蛋白质和脂肪的极化质膜结构域的维持 组合物对于有效的肾细胞功能至关重要。受体和离子的分布 这些细胞中的转运蛋白在一定程度上受到这些蛋白质内化的速度的调节。 从顶端和基底侧面的细胞表面。货物招募的基础机制 对于在哪里开始这个过程的笼络蛋白涂层坑，人们知之甚少。局域合成 磷脂酰肌醇4，5-二磷酸(PIP2)在细胞内的作用 内吞作用和非极化细胞表面PIP2水平的调节可以不同地影响 不同蛋白质的内化。这一提议的中心假设是心尖和 肾上皮细胞的基底外侧PIP2代谢独立地被选择性调节 从这些结构域调控依赖于笼蛋白的内吞作用。与这一想法一致的是， PI5-激酶的三种亚型(产生细胞表面PIP2的酶)是不同的 定位于极化的肾上皮细胞。我们建议的具体目标是确定 肾上皮细胞中PIP2的心尖池和基底侧池是否被独立调节 检测激动剂刺激G蛋白偶联后PIP2水平的变化 受体影响极化膜结构域的内吞作用；并确定如何 顶端定位的PI5-激酶mPI5KI？调节顶端的内吞作用。我们的研究结果 对我们理解极化细胞如何划分PI具有重要的意义 合成和分解代谢以及这一过程在正常信号转导过程中如何受到影响 肾脏疾病。

The maintenance of polarized plasma membrane domains with distinct protein and lipid compositions is critical for efficient renal cell function. The distribution of receptors and ion transporters in these cells is regulated in part by the rate at which these proteins are internalized from the apical and basolateral cell surfaces. The mechanisms that underlie cargo recruitment to clathrin coated pits where this process is initiated are poorly understood. Localized synthesis of phosphatidylinositol 4,5-bisphosphate (PIP2) at endocytic sites plays multiple roles in endocytosis, and modulation of surface PIP2 levels in nonpolarized cells can differentially affect the internalization of distinct proteins. The central hypothesis of this proposal is that apical and basolateral PIP2 metabolism in renal epithelial cells is independently regulated to selectively modulate clathrin-dependent endocytosis from these domains. Consistent with this idea, that the three isoforms of PI5-kinase (the enzymes that generate cell surface PIP2) are differentially localized in polarized renal epithelial cells. The specific aims of our proposal are to determine whether apical and basolateral pools of PIP2 are independently modulated in renal epithelial cells; to examine how changes in PIP2 levels upon agonist stimulation of G protein coupled receptors affect endocytosis from polarized membrane domains; and to determine how the apically localized PI5-kinase mPI5KI¿ regulates apical endocytosis. The results of our studies have important implications for our understanding of how polarized cells compartmentalize PI synthesis and catabolism and for how this process is affected during normal signaling and in renal disease.